Slow, nondiffusive dynamics in concentrated nanoemulsions

• Published in: Physical review. E, Statistical, nonlinear, and soft matter physics Vol. 75; no. 4 Pt 1; p. 041401
• Main Authors: Guo, H, Wilking, J N, Liang, D, Mason, T G, Harden, J L, Leheny, R L
• Format: Journal Article
• Language: English
• Published: United States 01.04.2007
• ISSN: 1539-3755
• DOI: 10.1103/PhysRevE.75.041401

Using multispeckle x-ray photon correlation spectroscopy, we have measured the slow, wave-vector-dependent dynamics of concentrated, disordered nanoemulsions composed of silicone oil droplets in water. The intermediate scattering function possesses a compressed exponential line shape and a relaxation time that varies inversely with wave vector. We interpret this dynamics as strain in response to local stress relaxation. The motion includes a transient component whose characteristic velocity decays exponentially with time following a mechanical perturbation of the nanoemulsions and a second component whose characteristic velocity is essentially independent of time. The steady-state characteristic velocity is surprisingly insensitive to the droplet volume fraction in the concentrated regime, indicating that the strain motion is only weakly dependent on the droplet-droplet interactions.